| C-1027 and bleomycin are two Streptomycete natural products possessing potent antitumor activity. Their pharmaceutical potential and stuctural complexity led us to invesitgate their biosynthetic pathways in hopes of elucidating novel mechanisms to produce new drugs. Sugar moieties, in particular, were considered a promising avenue of research due to their critical roles in the bioactivity of both C-1027 and bleomycin.; Sequence analysis of the two biosynthetic clusters revealed several genes proposed to be involved in sugar biosynthesis. Functions of individual genes were examined by biochemical characterization of their protein products, targeted gene disruption, and bioconversion experiments. An α-D-glucose thymidylyltransferase (SgcA1), dTDP-glucose dehydratase (SgcA), and dTDP-4-keto-6-deoxyglucose aminotransferase (SgcA4) were all biochemically characterized as enzymes involved in the biosynthesis of the C-1027 deoxyaminosugar.; The transamination reaction catalyzed by SgcA4 revealed fascinating insights into C-1027 deoxyaminosugar biosynthesis. Prior research demonstrates that epimerization and C-methyltransfer reactions act on dTDP-4-keto sugar intermediates before aminotransfer. However, SgcA4 acts on dTDP-4-keto-6-deoxyglucose indicating a novel mechanism for subsequent enzymes in C-1027 deoxyaminosugar biosynthesis. These insights were utilized to initiate combinatorial biosynthesis efforts towards the production of novel compounds based on bioactive scaffolds. |
